The use of lithium and lithium-ion batteries in electric vehicles and hybrid vehicles makes high demands of battery safety. Liquid electrolytes such as DMC/EC/LiPF6 are often flammable. Solid ceramic electrolyte materials, however, are only flame-retardant and have a high stability. However, solid ceramic electrolytes have a relatively low lithium-ion conductivity at room temperature in comparison with liquid electrolytes. Lithium ion-conducting compounds are discussed in the publications WO 2005/085138, WO 2009/003695 A2, WO 2010/090301 A1 and EP 2 159 867 A1, for example.